BACKGROUND Nitric oxide (NO) is rapidly oxidised in humans to nitrite and nitrate, with nitrate being present in much greater abundance. These oxidation products can be recycled back into nitric oxide via a complex entero-salivary pathway, thus preserving NO activity. Approximately 65% of circulating nitrate is excreted in the urine in 48 h, with the excretory pathway of the remainder unknown. The effect of declining renal function on nitrate clearance is unknown METHODS: Forty five subjects, 21 M, 24F, median age 69 (range 27-75 years) with renal function assessed by CKD-EPI eGFR between 9 and 89 ml/min/1.73 m2 completed the study. Following a 24 h low nitrate diet a microplate spectrophotometric method was employed to measure plasma nitrate concentration and 24 h urinary nitrate excretion were measured to determine renal nitrate clearance. RESULTS There was a strong positive correlation between urinary nitrate clearance and eGFR, (Spearman R = 0.7665, p < 0.0001) with a moderate negative correlation between plasma nitrate concentration and CKD-EPI eGFR, (Spearman's R = -0.37, p = 0.012). There was a trend between fractional excretion of nitrate and CKD-EPI eGFR (ml/min/1.73 m2) Spearman's R 0.27, p = 0.07 though this did not reach statistical significance. Plasma nitrate concentration and serum creatinine concentration were positively correlated, Spearman's R = 0.39, p = 0.008. CONCLUSIONS We have observed a strong positive association between renal nitrate clearance and renal function such that plasma nitrate rises as renal function falls. Fractional excretion of nitrate appears to decline as renal function falls. As such, urinary nitrate excretion is unlikely to be a reliable marker of endogenous NO synthesis in settings where renal function is altered.

中文翻译：

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慢性肾脏疾病中肾脏硝酸盐的清除。

背景技术一氧化氮（NO）在人类中被快速氧化为亚硝酸盐和硝酸盐，其中硝酸盐的含量更高。这些氧化产物可通过复杂的肠唾液途径循环回一氧化氮，从而保留NO活性。在48小时内，大约65％的循环硝酸盐从尿液中排出，其余的排出途径未知。方法未知：肾功能下降对硝酸盐清除率的影响方法：四十五名受试者，年龄分别为21 M，24 F，中位年龄69岁（范围27-75岁），并通过CKD-EPI eGFR评估肾功能在9和89 ml / min / 1.73之间平方米完成了研究。在低硝酸盐饮食24小时后，采用微孔板分光光度法测定血浆硝酸盐浓度，并测定24小时尿中硝酸盐排泄量，以测定肾脏硝酸盐清除率。结果尿液硝酸盐清除率与eGFR之间存在很强的正相关（Spearman R = 0.7665，p <0.0001），而血浆硝酸盐浓度与CKD-EPI eGFR之间存在中等程度的负相关（Spearman's R = -0.37，p = 0.012） 。硝酸盐的排泄量与CKD-EPI eGFR（ml / min / 1.73 m2）Spearman R = 0.27，p = 0.07之间存在趋势，尽管这没有统计学意义。血浆硝酸盐浓度和血清肌酐浓度呈正相关，Spearman的R = 0.39，p = 0.008。结论我们观察到肾硝酸盐清除率与肾功能之间有很强的正相关性，因此血浆硝酸盐随肾功能的下降而升高。硝酸盐的部分排泄似乎随着肾功能下降而下降。因此，